1. Field of the Invention
The present invention relates to a semiconductor device and a method for driving the semiconductor device. Note that in this specification, the semiconductor device means a semiconductor element itself or a device including a semiconductor element. As such a semiconductor element, for example, a thin film transistor can be given. Therefore, the semiconductor device includes a liquid crystal display device and the like.
2. Description of the Related Art
In recent years, metal oxides having semiconductor characteristics (hereinafter, referred to as oxide semiconductors) have attracted attention. The metal oxides having semiconductor characteristics can be applied to transistors (e.g., Patent Document 1 and Patent Document 2).